Roubo flattening question

Today, I flattened the bottom of what will end up being the top of a Roubo style bench. I did the bottom before the top so that I had a nice, true surface to cut the mortises for the legs. What I’m wondering now is, is it worth flipping it over and doing the top side now, or should I wait until the bench is completely assembled before doing the top? I’m curious if the slab could move from the cutting of the big (2.5×2.5×5) leg mortises.

If its just going to need to be flattened again, I’d rather wait and just use the bottom as-is for now. But if it won’t really move, I’d like to do the top now so I can get the wagon vise all done. I think that would be very helpful to have for finishing up the legs.

Its doug fir, one big slab, 2’ x 8’ x 4.5”. Ive had this wood for about 6 months, so its certainly done adjusting to the shop. I’m just concerned about the milling forces pulling it out of whatever alignment it’s in now.

I’m working on my Roubo right now also. I just rough planed the top side for now. I think there will be too many tool marks and other issues to worry about the top side until after I flip it over for good.